1. Field of the Invention
The present invention relates to closures suitable for use with flexible bags, such as sandwich bags made out of polyethylene film. Related applications assigned to the same assignee as this application include the following copending and concurrently filed applications: "Adhesive Bag Closure that Opens Easily By Hand But Resists Opening By Contents", Ser. No. 335,800, filed Dec. 30, 1981, abandoned; "Protective Strip for Z-Fold Bag Closure", Ser. No. 335,955, filed Dec. 30, 1981, U.S. Pat. No. 4,410,130 "Manufacturing Process for Channel Seal", Ser. No. 365,814, filed Apr. 5, 1982, U.S. Pat. No. 4,392,897; and "Laminated Pressure Sensitive Adhesive Systems for Use in Plastic Bags", Ser. No. 335,799, U.S. Pat. No. 4,415,087, filed Dec. 30, 1981, the last application being incorporated by reference herein.
2. Brief Description of the Prior Art
A number of closure arrangements have been used to seal and/or close plastic bags such as those used for sandwiches, garbage containers, and other household uses. These previous attempts include the so-called profile bags where the closure comprises one or more sets of mating channels. Each channel may be formed as an integral part of the bag or fabricated as a separate piece and attached to the bag. One example of a profile closure is the Zip-loc storage bag as found in U.S. Pat. No. 28,969 to Naito. For examples of other profile bags see U.S. Pat. No. 3,226,787 to Ausnit and U.S. Pat. No. 3,060,985. As seen in U.S. Pat. No. 4,186,786 to Kirkpatrick, colored channels have been used to allow the user to more easily detect complete occlusion of profile bag openings. In order to achieve satisfactory use with profile bag closures, however, the mating members must fit properly and be aligned correctly. It may take several attempts at closing the bag before proper registration of the mating members is finally achieved. Bags with profile closures also tend to be an expensive choice for uses which do not require the containment of liquids.
Other types of bag closures use one or more adhesive strips. Problems with such adhesive closures include weak shear strength because the exposed adhesive for a strip must be selected to be weak enough so that it does not undesirably stick to other bags while on a roll or in a box.
An attempt to combine a profile closure with an adhesive may be seen in U.S. Pat. No. 3,339,606 to Kugler. The releasable closure in the Kugler patent comprises a tongue on one member and a groove on the other member where the tongue is of a thickness less than the width of the PG,5 groove and wherein a releasable pressure sensitive adhesive is provided to keep the tongue within the groove. This structure, however, still requires registration of mating channels.
Attempts have also been made to protect the adhesive strip until the bag is used. In U.S. Pat. No. 3,420,433 to Bostwick a closure flap having an adhesive applied thereto is folded or overflapped upon itself to form a protective enclosure for the adhesive prior to the use of the bag. In U.S. Pat. No. 3,990,627 to Olson (and assigned to the same assignee as this application), a Z-fold adhesive closure for bags is disclosed wherein the adhesive strip is covered by the upper portion of the bag's front wall until ready for use. It is difficult, however, to find an adhesive which is easy to apply, which is strong enough to form an effective seal upon closure, but which does not cause undesirable problems by sticking to other bags or miscellaneous surfaces.
In the pressure sensitive adhesive art, the solution to the problem of sticking during shipment and storage has been to provide a release layer over the pressure sensitive adhesive. For example, pressure sensitive plastic tapes have a release layer which impedes the sticking of the adhesive to the plastic of the adjacent layer in the roll. This approach is not desirable on closures for plastic bags because of expense and difficulty in manufacture.
Thus, it is an object of the present invention to provide closures suitable for use with plastic bags wherein the closures are able to effect a satisfactory seal as needed, without sticking to other bags while in storage. It is a further object of this invention to provide a closure suitable for use with flexible bags where a more powerful adhesive may be utilized without interfering with the storage of the bag on a roll. It is yet another object of this invention to provide closure seals for use with flexible bags wherein mating contact between flap and front is not needed to effect closure. It is a further object of this invention to provide a flexible bag with an openable and resealable closure. It is another object still to provide a closure for a flexible bag in which the bag may be fitted to the object contained therein and the closure may be used to maintain the fit. It is another object of this invention to provide a flexible bag with a resealable closure which exhibits good shear strength. These and other objects of the invention will be apparent from the following description.